Method and apparatus for continuous devulcanization of rubber

Abstract

An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material has an ultrasonic exposure portion including a body forming an exposure channel through which particles of the material flow and an ultrasonic generator including a horn extending generally traverse to the direction of the material flow. The apparatus also has a preconditioning portion for feeding the particles to the ultrasonic exposure channel. The method for devulcanizing vulcanized rubber or crosslinked polymeric material comprises the steps of preconditioning and feeding particles of the material, including heating the particles; feeding the particles through a pressurized exposure channel; and exposing the particles to ultrasonic energy within the exposure channel with an ultrasonic wave propagated in a direction traverse to the direction of the channel to effect devulcanization by breaking chemical bonds in the material.

What is claimed is: 
     
       1. An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material, comprising: an ultrasonic exposure portion including a body forming at least one exposure channel through which particles of the material flow, the channel extending helically through the body, and   at least one ultrasonic generator associated with the channel, the ultrasonic generator including a horn extending generally transverse to the direction of the channel at the location of the generator; and   a preconditioning portion for feeding the particles to the ultrasonic exposure channel.     
     
     
       2. An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material as recited in claim 1, comprising in addition a postconditioning portion connected to the ultrasonic exposure portion for receiving material from the ultrasonic exposure portion. 
     
     
       3. An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material, comprising: an ultrasonic exposure portion including a body having a cylindrical opening therethrough, at least one groove being formed on the interior of the opening, the groove extending in a helical direction along the interior surface of the opening,   a cylindrical core adapted for rotation within the opening, the exterior of the core and the groove forming a helically-extending exposure channel through which particles of the material flow, and   an ultrasonic generator associated with the channel and including a horn extending generally transverse to the direction of the channel at the location of the generator;     a preconditioning portion connected to the ultrasonic exposure portion for feeding the particles to the ultrasonic exposure portion.   
     
     
       4. An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material as recited in claim 3, wherein the preconditioning portion includes a barrel with a feedscrew rotating within the barrel to feed the particles to the ultrasonic exposure portion. 
     
     
       5. An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material as recited in claim 3, wherein the core is attached to the feedscrew to rotate therewith. 
     
     
       6. An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material as recited in claim 3, comprising in addition a postconditioning portion connected to the ultrasonic exposure portion for receiving material from the ultrasonic exposure portion. 
     
     
       7. An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material as recited in claim 6, wherein the postconditioning portion includes a barrel and a feedscrew extension adapted to rotate within the barrel to convey material from the ultrasonic exposure portion. 
     
     
       8. An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material as recited in claim 7, wherein the feedscrew extension is attached to the feedscrew to rotate therewith. 
     
     
       9. An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material, comprising: an ultrasonic exposure portion including a body forming at least one exposure channel through which particles of the material flow, and   at least one ultrasonic generator associated with the channel, the ultrasonic generator including a horn extending generally transverse to the direction of the channel at the location of the generator;     a preconditioning portion for feeding the particles to the ultrasonic exposure channel; and   a postconditioning portion connected to the ultrasonic exposure portion for receiving material from the ultrasonic exposure portion and cooling said material without exposing the material.   
     
     
       10. An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material as recited in claim 9, wherein the preconditioning portion includes a barrel with a feedscrew rotating within the barrel to feed the particles to the ultrasonic exposure portion. 
     
     
       11. An apparatus for devulcanizing vulcanized rubber or crosslinked polymeric material, comprising: an ultrasonic exposure portion including a body having a cylindrical opening therethrough, at least one groove being formed on the interior surface of the opening,   a cylindrical core adapted for rotation within the opening, the exterior of the core and the groove together forming a helically-extending exposure channel through which particles of the material flow, and   an ultrasonic generator connected to the channel at a point of intersection, the ultrasonic generator including a horn extending generally transverse to the direction of the channel at the point of intersection;     a preconditioning portion connected to the ultrasonic exposure portion for feeding the particles to the ultrasonic exposure portion, the preconditioning portion including a first barrel having heaters for heating the particles as they travel through the first barrel, and   a feedscrew adapted to rotate within the barrel to feed the particles to the ultrasonic exposure portion, the feedscrew connected to the core to rotate therewith; and     a postconditioning portion connected to the ultrasonic exposure portion for receiving material from the ultrasonic exposure portion, the postconditioning portion including a second barrel having cooling channels for circulation of a cooling fluid to cool the material as it travels through the second barrel, and   a feedscrew extension adapted to rotate within the barrel to convey material from the ultrasonic exposure portion, the feedscrew extension connected to the core to rotate therewith.     
     
     
       12. A method for devulcanizing vulcanized rubber or crosslinked polymeric material, comprising the steps of: preconditioning and feeding particles of the material, including heating the particles;   feeding the particles through a pressurized helically-shaped exposure channel; and   exposing the particles to ultrasonic energy within the exposure channel with ultrasonic waves propagated by an ultrasonic generator connected to the channel, the ultrasonic wave propagated in a direction transverse to the direction of the channel and effecting devulcanization by breaking chemical bonds in the material.   
     
     
       13. A method for devulcanizing vulcanized rubber or crosslinked polymeric material as recited in claim 12, wherein the particles are fed through an exposure channel formed by a central cylindrical core rotating within a cylindrical opening of a body with the opening having a groove on the interior surface thereof, the channel being formed between the groove and the exterior of the core. 
     
     
       14. A method for devulcanizing vulcanized rubber or crosslinked polymeric material as recited in claim 13, wherein the particles are preconditioned and fed by a feedscrew, the core being connected to the feedscrew to rotate therewith.